Paste function is not working with Firefox

### Is this a hackmd.io issue?

- [x] Yes, the bug happens on https://hackmd.io
- [ ] No. If it's a self-hosted CodiMD instance, please fire up the issue in the repo of CodiMD: https://github.com/hackmdio/codimd

### What's the problem
It can copy the text to other , but **paste** didn't work as well

#### Current behaviour

Provide steps to reproduce:

1. Just go to edit panel of the note
2. Copy and paste any text

#### Expected behaviour

it should paste the text from clipboard to the note

#### Environment

I use HackMD on:

**Desktop**
- OS: Windows 10 Pro
- Browser: Firefox
- Version: v112